High-frequency heating and compression apparatus



1950 E. c. HANSON ET AL 2,497,570

HIGH-FREQUENCY HEATING AND COMPRESSION APPARATUS Filed June 1, 1946 Fig. I.

HIGH FREQUENCY Pol YER aouncs V/lCl/UM PUMP Inventors: Kari C. Hansen. Dcmmd E. Watts,

Patented Feb. 14, 1950 UNITED STATES PATENT OFFICE .HIGH-FREQUENCY HEATING AND COMPRESSION APPARATUS 'Earl C.*Hanson,i.Cleveland, Ohio, and Donald E. Watts, De Witt,- N. ;LY., assignors to. General Electric Companypa corporation of.

New York Application June 1, 1946;"Scrial No. 673,725

.6 Claims.

Our' invention relates to 'high frequency elec- .tric heating-and compression apparatus-more particularlyto heating apparatus utilizing a resonant or nonresonant' chamber in which the material is heated; and has for its object simple and reliable apparatusicr heating material under pressure.

In carrying: out our invention in one form we provide :a chamber havingwalls' iormedof an electrically conducting. material such as copper and oi such size as tobe tuned'to' the frequency of the supplysource,"in=which chamber the material is heatedand compressed. Our. invention is useful in the heating ordielectric organic and inorganic materials includingxpaper, fabrics, food products; synthetic resins, rubber, etc.

The resonant or nonresonant heatingchamber mayxalsoconstitutesa mold in which theheatd material is compressed into.adesired form. For

example, an unvulcanized rubber mixture may be I heatedto vulcanize. itandcompressed. into a desired form in the chamber.

For .a more complete understanding of our :in-

:vention reference should. be 'had to' the accompanying drawing Fig. 1 of which is asectional r view of high frequency heating apparatus embodying :our invention; Fig. 2. is .a. view similarto Fig. .1 showing a modified form. of our invention,

while Fig. :3 -is: a view in. perspective of .a. modified form of our invention.

We'have shownzour invention inFig. las ap- .plied" to theheatingofsa plasticmaterial prior to itszinjection into aimolding'machine. In this form-of our invention we'provide a tubular member I made of electrically conductingwmaterial,

such as. copperforcontaining a plastic or synthetic resin material 2 to. be heated. A fixed end of the chamber isformed by a partition wall. 3 secured in place in'thetubular member by- -a flange3', the wall 3-being madeof a suitable dielectric material having-a low power factor as compared with the plastic material 2 such as low power factor glass. The opposite end of the heating chamber is formedby a plunger 4 made of copper'to which is'secured aiacing plate- 5 made of low power factor glass or. other low power .loss material,'the-.-plunger 4 and'- plate:5 .fitting slidably in the tubular member Landbeing movable therein by suitable means not shown to compress the material 2.

Theplates 3 and Sserve to position the material 22in the chamber! relative to. the end walls .of the chamber for effective heating by the electric and magnetic fields in the chamber.

Electric power-at a suitable .highfrequency :is

high frequency oscillating :magnetic and electric fieldsaresetvup in the chamber by'meansof which heat is generated inzthe material 2. The device Bis preferably located about one-half wage length from thelower end of. the waveguide. It will' be observed that. the partition 3 forms a space for the power coupling device 8- between the partition andithe lower end wall of the chamber.

In order toiprovide for thexpropagation of electricwaves in.- the wave guide and chamber and energy oscillation back and forth from electric to magnetic fieldsat'the frequency of the supply source, the diameters. of the *wave guide and the chamber aresele'cted'tohave a predetermined relation. to the'wa've: length of the. supply frequency, i; e.,.0.585 wave length or greater. For

example, with airequency'of 2000 megacycles .and wave length of 15 centimeters the inside diameterof the waveguide Bis at least 8.775centimeters while the diameter ofthe chamber l is much greater in order to contain the desired :amount of material 2.

In.the:operation of the heater of Fig. 1 the plastic material 2 is put into the chamber 1 after :firstremoving the plunger 4 and plate 5. The :plunger and plate are then inserted and a suitable pressure 1 applied.

When the plastic material: isrheated touthe desired extent it becomes liquid enough to 'flowout of the spout H which feeds the material, for eXampIe to a molding machine, not shown The movement of the plunger may decreasetherate ofheating and if desired the frequency of the .supply source can be changed to restore generation of heat.

In Fig. 2 we have shown a modified form of our invention for .use in the processing of food products by combined. heatand pressure. This heating apparatus comprises a cylindrical member l2 forming aresonant or nomesonant heating chamber with a fixed low-loss glass wall or other low-loss material l3 at one end and a plunger M in. the other end, these parts being similar in construction to the corresponding parts. of Fig. 1 and power coupling meansbeing provided between the wall l3 and the left-hand .endoi the chamber as shown in Fig 1. A. plu- -tachable means is cured article. :ternaI configuration of the parts 20 and 2i and rality of apertures I5, 16, and I! are provided in the lower wall of the chamber for the escape of liquids pressed out of the food products in the chamber.

In the operation of this form of our invention the plunger [4 is moved inward by the application of a predetermined force thereto while the food products in the chamber are heated to a predetermined temperature and maintained at that temperature to facilitate the compression of theproducts and their drying. Vapors givenoff by the products may be removed and condenser I8 connected to the chamber by a pipe [9.

We contemplate that by means of the apparaby a vacuum pump tus disclosed in Fig. 2 compressed and dehydrated food pellets may be made. Also juices and oils,

may be extracted from the compressed products such as grapes, sugar beets, oranges, cotton seeds, peanuts, fish, etc.

In the modified form of our invention shown Fig. 3 a heating chamber similar to that disclosed in Fig. 1 is provided but adapted to form a'compression mold for forming articles from various materials such as thermal setting synthetic resins and for vulcanizing and forming rubber articles. In this case the heating cham- 'beris formed in at least two parts which can 'be separatedto remove the formed and heat treated article.

As shown, the heating chamber is formed by two semi-cylindrical parts and 2| suitably detachably secured together as by bolts 22 and 23, although preferably quickly deprovided for securing the parts together.

'In the form of Fig. 3, as in the form of Figs. 1 and 2, the plunger 24 is depressed as the material in the chamber is heated and cured. After the 'completion of the heat treating and forming operation the chamber is opened by separating the parts 20 and 2| for the removal of the molded and It will be understood that the inof the low-loss glass (or other low-loss material) end parts 25 and 26 is such as to give the desired shape of the molded part. It will be understood that power coupling means as shown in Fig. 1 is provided between the wall 26 and the lower end of the chamber.

Obviously, when the heating chamber is filled with material, tuning of the chamber with the supply source will be broad and a resonant condition may not exist.

I While we have shown a particular embodiment of our invention it will be understood of course thatwe do not wish to be limited thereto since many modifications may be made and we therefore contemplate by the appended claims to cover any such modifications as fall within the true spirit and scope of our invention.

What we claim as new and desire to secure by Letters Patent of the United States, is:

1. High frequency electric heating and compression apparatus comprising an electronic 0S- cillator generator for supplying high frequency "power, walls made of electrically conducting material forming a heating and compression chamber closed at one end, power transmission means connecting said generator with said chamber including power coupling means extending through one of said walls into said chamber for producing high frequency oscillating fields in said chamber for the generation of heat in a material to be heated in said chamber, a partition wall of dielectric material extending across said chamber terial forming a heating and compression chamber closed at one end by an end Wall, power transmission means connecting said generator with said chamber including power coupling means extending through said end wall into said chamber for producing high frequency oscillating fields in said chamber for the generation of heat in a material tobe heated in said chamber, a partition wall of dielectric material extending across said chamber adjacent said end wall thereby to provide a space for said power coupling means between said partition wall and said end wall, said partition wall being made of a material having a low power factor as compared with the material to be heated, and a plunger made of electrically conducting material in the other end of said chamber movable to compress the material in said chamber against said partition wall.

3. High frequency electric heating and compression apparatus comprising an electronic oscillator generator for supplying high frequency power, a tubular member of electrically conducting material forming a heating and compression chamber having a diameter at least as great as .585 times the wave length of said generator, an

electrically conducting end wall closing one end J provide a space for said power coupling means between said partition wall and said end wall, said partition wall being made of a material having a low power factor as compared with the material to be heated, and a plunger made of electrically conducting material closing the other end of said chamber movable to compress the material in said chamber against said partition wall.

4. A combined electric heater and mold for heating and forming dielectric materials comprising an electronic oscillator generator for supplying high frequency power, walls made of electrically conducting material forming a heating and mold chamber closed at one end by an end Wall, power transmission means connecting said generator with said chamber including power coupling means extending through said end wall into said chamber for producing high frequency oscillating fields in said chamber for the generation of heat in a dielectric material in said chamdielectric material extending across said chamber adjacent said end wall thereby to provide a space for said power coupling means between said partition wall and said end wall, said partition wall being made of a material having a low power factor as compared with the dielectricmaterial to be heated, and a plunger made of electrically conducting material closing the other end of said chamber movable to compress the dielectric material in said chamber against said partition wall thereby to form the material.

5. A combined electric heater and feeding device for plastic dielectric materials comprising an electronic oscillation generator for supplying high frequency power, walls made of electrically conducting material forming a heating and compression chamber closed at one end, power transmission means connecting said generator with said chamber including power coupling means extending through one of said walls into said chamber, a partition wall of dielectric material extending across said chamber adjacent said one wall thereby to provide a space for said power coupling means between said partition wall and said one wall, said partition wall being made of a material having a low power factor as compared with the dielectric material to be heated, pressure applying means made of electrically conducting material closing the other end of said chamber, operable to compress the dielectric material in said chamber, and a spout connected to said chamber through which the heated dielectric material can be forced by said pressure applying means after it has been heated to liquefy it.

6. A combined electric heater and feeding device for plastic dielectric materials comprising an electronic oscillation generator for supplying high frequency power, walls made of electrically conducting material forming a heating chamber closed at one end by an end wall, power transmission means connecting said generator with said chamber including power coupling means extending through said end wall into said chamber, a partition wall of dielectric material extending across said chamber adjacent said end wall thereby to provide a space for said power coupling means between said partition wall and said end wall, said partition wall being made of a material having a low power factor as com- 5 pared with the dielectric material to be heated,

a plunger made of electrically conducting material closing the other end of said chamber movable to compress the dielectric material in said chamber against said partition wall, and a spout 10 connected to said chamber adjacent said partition wall through which the heated dielectric material can be forced by movement of said plunger after it has been heated to liquefy it.

EARL C. HANSON.

DONALD E. WATTS.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,930,169 Halvorson et al. Oct. 10, 1933 2,167,544 De Bats et al July 25, 1939 2,197,122 Bowen Apr. 16, 1940 2,232,179 King Feb. 18, 1941 2,259,313 Mouromtseff Oct. 14, 1941 2,341,617 Hull Feb. 15, 1944 2,364,526 Hansell Dec. 5, 1944 2,370,161 Hansen Feb. 27, 1945 2,370,624 Gillespie Mar. 6, 1945 2,398,606 Wang Apr. 16, 1946 2,436,999 MacMillin et al Mar. 2, 1948 OTHER REFERENCES Physical Behavior of Wave Guides, Electronics, March 1943, pages 76-80, particularly pages '79 and 80. 40 

